The present invention relates to a returnable dunnage assembly for use in shipping a relatively complex, machined metal member, and more particularly, to such a dunnage assembly which is suitable for use in xe2x80x9cover the highwayxe2x80x9d shipment of such machined members.
As is used herein, the term xe2x80x9creturnablexe2x80x9d in regard to the dunnage assembly of the present invention will be understood to mean that the dunnage assembly may be returned, for example, to the original point of shipment of the machined member, and the assembly may then be reused subsequently for shipping additional, identical machined members. As is well know to those skilled in the art, it is essential that dunnage of the type to which the present invention relates be reusable a number of times, in order to spread the cost of the dunnage assembly over a number of parts, thus reducing the total cost of shipment attributable to each machined part.
Although the present invention would have application in connection with the shipment of many types of manufactured items, it is especially advantageous when used in connection with the shipment of relatively complex, machined metal castings, and will be described in connection therewith. Furthermore, but by way of example only, the present invention was developed in connection with a need to ship machined cylinder heads, for assembly as part of internal combustion engines, and will be described in connection therewith. Conventionally, machined cylinder heads (whether cast iron or cast aluminum) have been shipped to various locations within the particular engine plant in relatively rigid plastic containers, with each cylinder head being somewhat loosely received within the container (also sometimes and hereinafter referred to as a xe2x80x9ctrayxe2x80x9d). Typically, the tray might be configured to hold a number of cylinder heads, for example, four cylinder heads in one tray.
Such plastic trays have been generally satisfactory when the cylinder heads were merely being shipped within a single engine plant, or within an engine plant complex. However, it has been found that the use of such trays is not acceptable in situations in which the cylinder head is machined at a first location, and is then shipped from that first location to a second location, such as the engine assembly plant, wherein the containers of cylinder heads must be shipped a long distance over-the-highway, typically by truck.
Among the problems associated with the over-the-highway shipment of machined cylinder heads, using the plastic trays intended only as in-plant dunnage, is that the heads are permitted to move within the plastic tray, and the various sharp edges defined by the machined surfaces engage, or make contact with, interior surfaces of the plastic tray and generate plastic shavings, shaved from the tray, as the tray vibrates during over-the-highway shipment. The problem with the generation of plastic shavings during shipment is not primarily the potential damage to the plastic tray, although that could eventually become a problem. Instead, the immediate, and greater problem with the generation of plastic shavings during shipment is that such shavings tend to adhere to the machined member, and in particular, tend to adhere to the machined surfaces. Thus, when the cylinder head is received at the engine assembly plant, it is necessary to wash the cylinder head, or in some other way remove the shavings, before the head is assembled to the engine block. Such an additional process step, which is not normally necessary when the head is merely being shipped in-plant, is undesirable because it represents additional handling of the cylinder head, and therefore, additional cost of assembly of the engine.
It is also known to ship machined metal members, such as cylinder heads, by wrapping the members in a sort of plastic xe2x80x9cshrink wrapxe2x80x9d packing material. Although such a packing material may be effective in eliminating the problem of the generation of plastic shavings, such a packing/dunnage arrangement for cylinder heads is not acceptable, primarily because, once the cylinder head and packing material combination is received in the engine assembly plant, the cylinder heads must first be unpacked and then placed within in-plant dunnage for subsequent handling. This again adds an additional, otherwise unproductive, operation or step which is undesirable.
As is well know to those skilled in the engine assembly art, the major parts of an engine, such as the cylinder block and the cylinder head(s), are typically handled by assembly robots in the engine assembly plant. Therefore, any dunnage assembly used for shipping the cylinder heads should preferably be designed such that, once the dunnage assembly is within the assembly plant, an assembly robot can grasp the cylinder head and lift it out of a dunnage tray, without any preparatory steps being required, other than sensing the location of the tray. This objective requires that the cylinder head be very accurately located within the tray. For example, the location of the cylinder head within the tray must be within the range of about +/xe2x88x920.015 inches relative to the tray, in order for the assembly robot to be able to grasp the head, on a consistent, repeatable basis.
Another known, prior art dunnage arrangement which has been used for shipping engine cylinder heads involves an outer, tray-like member which is a bolted-together assembly of a number of different members. The outer member receives and supports a number of individual support members, each of which is bolted to the outer member. The support members are plastic members, molded from the same type of relatively rigid, plastic material as has been used typically for the prior art trays. Thus, if the above-described dunnage arrangement is utilized for over-the-highway shipment, it is likely that the xe2x80x9cshavingsxe2x80x9d problem will occur, but in this case, the shavings would be removed from the individual support members, rather than from the outer tray. In addition, the rigid support members, bolted to the rigid outer member, are not likely to provide both the desired anti-vibration support and the accurate location for purposes of employing the assembly robot.
Accordingly, it is an object of the present invention to provide a returnable dunnage assembly especially adapted for shipping relatively complex, machined metal members which will overcome the above-described problems of the prior art.
It is a more specific object of the present invention to provide such a dunnage assembly which will permit over-the-highway shipment (or some other type of shipment which results in substantial vibration) without the resulting vibration causing the generation of plastic shavings from the container in which the machined member is immediately disposed.
It is a more specific object of the present invention to provide a dunnage assembly which accomplishes the above-stated objects, while at the same time being capable of positioning the machined metal member very accurately within the outer container, thus being adaptable to the use of automated material handling equipment.
The above and other objects are accomplished by the provision of a returnable dunnage assembly for a relatively complex, machined metal member having a particular, lower portion external profile. The dunnage assembly includes a relatively rigid container defining an internal configuration larger than the lower portion external profile of the member.
The dunnage assembly is characterized by a relatively flexible, conformable insert member removably disposed within the internal configuration of the container and having an external configuration closely spaced apart within the internal configuration of the container. The insert member defines an internal profile configured to be in engagement with the lower portion external profile over at least a major portion thereof, as that term will be defined subsequently. The insert member comprises a material operable to withstand being in engagement with the machined metal member during movement of the dunnage assembly without the engagement causing the generation of shavings from the insert member.
In accordance with another aspect of the invention, the dunnage assembly is characterized by the fit of the external configuration of the insert member within the internal configuration of the container, and the fit of the lower portion external profile within the internal profile of the insert member being within a relatively narrow tolerance to facilitate insertion of the machined member into, or removal from the container by automated material handing means.